1. Field of the Invention
This invention relates to devices for dispensing a plurality of fluids in a precise ratio to each other. More particularly, the invention disclosed herein relates to an improved fluid-driven liquid proportioning pump that effects the positive displacement of the fluids involved. While adaptable to a number of diverse uses, the methods and apparatus of the present invention have ready applicability in the field of mixing and dispensing carbonated beverages.
2. Background Art
Many aspects of industrial processing and consumer merchandising require the continuous, precise dispensing and mixing of a plurality of constituent fluids into a desired product. This is the case in the manufacture of paints, pesticides, fertilizers, and industrial sealants, as well as in the preparation of foods and pharmaceutical, such as margarine, syrups, medicines, toothpaste, and cosmetic preparations In the retial area the dispensing of individual constituent fluids for mixture into a final consumable product is prominent in relation to the retailing of carbonated and other syrup-based beverages and juices.
While the methods and apparatus of the present invention finds utility in each of the above-named and other fields, an immediate application of the present invention resides in meeting the demand in the carbonated beverage industry for an improved manner by which the constituent fluids of such beverages may be dispensed and mixed into a consumer product having narrow specifications that are dictated by desired product taste.
In the production of carbonated beverages, such as cola-type beverages, orange drinks, lemonade drinks, and the like, aromatic flavoring agents in liquid form, such as syrups and concentrates, are metered and combined with predetermined quantities of carbonated water. Typically, the carbonated water is pressurized and mixed with the syrups to form a finished beverage that may be dispensed either into reusable or disposable containers.
This process of dispensing and blending into a final mixture the proper quantities of each fluid in a manner capable of satisfying the sensitized tastes of the consuming public has been rendered moire complicated in recent years by two developments. Firstly, the public preference for artificially sweetened carbonated beverages has increased dramatically. Secondly, the perceived necessity to replace the artificial sweetener saccharin with another has resulted in a widespread shift by the foods industry to use of the artificial sweetener, aspertaime, commonly marketed under the trademark NUTRASWEET.RTM.. Unfortunately, aspertaime has a relatively short shelf-life, after which the flavor of the sweetener undergoes markedly noticeable alteration.
This fact about aspertaime has lead to the practice in the soft drink industry of separating the sweetening element from the aromatic syrups, so that the turnover of sweetener supplies can be accelerated. Accordingly, in dispensing and blending the components of a carbonated beverage that is to contain aspertaime, it is now necessary to blend, not merely two different constituent fluids, but three: carbonated water, an aromatic syrup, and sweetener.
The effort to develop fluid proportioning devices suitable for metering more than two constituent fluids only cast in a harsher light the drawbacks of the devices previously developed toward the dispensing of two constituent fluids. Prior devices were complicated, requiring plural conduits, complex valving, and forms of involved linkages for effecting coordination between the operation of otherwise independent dispensing mechanisms. DEvices which fail to physically integrate the dispensing mechanisms necessitated the use of additional mechanical systems for coordinating the necessarily separate dispensing functions. This added to the complexity of dispensing devices, resulting in a need for require increased maintenance. The resort to electrical drive motors to overcome the need for motive power only complicated the proportioning pumps by adding thereto another system needing its own separate maintenance and isolation for safety and operational purposes.
Many proportioning pumps were reciprocating in nature, but were successful in dispensing constituent fluids in one direction of their reciprocating motion. This produced uneven flow and irregular ratios of the constituent fluids involved in each cycle of operation.
The actual proportioning aspect of such devices presented several problems. Many simply were not accurate, so that a user was faced with unreliability in preparing a final product. The proportioning function was frequently effected by valving external to the mechanism by which constituent fluids were actually advanced through the system. Such external valving itself comprised a separate system of mechanical operation requiring its own maintenance and coordination.
In many instances the proportioning ratio of a given device was either fixed, or if not fixed, was extremely difficult to alter, requiring in most instances disassembly and reassembly in a trial-by-error method. The effort to integrate such proportioning mechanisms resulted in some devices having the proportioning aspects built into the heads of the pistons that are used to advance the constituent fluids. In this location, any alteration of the proportioning ratio was at best difficult to achieve without suffering the expense of substantial down time.
A significant problem in prior proportioning pumps was that the plurality of fluids involved necessitated the incorporation into the proportioning device of a number of dynamic seals. In many cases, of necessity, one or more of these seals was exposed on one side to the atmosphere, tending to age it rapidly due to drying. The concomitant need for replacement and repair of such components is readily predictable.
Ultimately, prior fluid proportioning pumps were complicated assemblages of separate mechanical systems. Each separate component systems required its own maintenance. Intervening systems were necessary for effecting coordinated operations. In the effort to streamline such devices, designers were faced with two conflicting tendencies. Either the subsystems ancillary to that used to advance constituent fluids would be located external to the advancement system, where they would be relatively easily accessible for maintenance and adjustment purposes but relatively difficult to coordinate in any simple manner, or such subsystems could be integrated into the mechanical structure of the fluid advancement subsystem rendered them difficult to access, while possibly more easy to coordinate.
All such drawbacks existed in proportioning pumps used with just two constituent fluids. The need for proportioning pumps which could effectively dispense more than two fluids exacerbated known problems. Additional constituent fluids required additional subsystems for coordination and proportioning. Devices grew more complex, rather than simpler, as would have been desired. No method or apparatus was available which both coped effectively with additional constituent fluids and simplified the number of subsystems and components involved.